Hey, so I'm a solid US 10D and I comfortably wear a Carmina UK9 in the Forest last, 43 in Vass F last and I just fit into a UK 9E in the C&J 348 last. (My left foot is OK but my slightly larger right foot is at about max capacity by the pinky toe.) I'm including the C&J's as I'm assuming it's the closest shoe I have last wise in relation to the Simpson. So, the question begs, will a 9 UK Simpson work for me or would I need to size up to a 9.5?
Yes, size up to UK9.5.